This invention relates generally to pipe end finishing machinery and more particularly to machinery and methods for boring and turning upset pipe ends.
Metal drill pipes and tubing, such as used for oil or gas wells, are manufactured in sections in rough form with upset or thickened pipe ends. These upset pipe ends must have their inside and outside diameters machined or bored and turned before they can be used in the field to connect adjacent pipe sections.
Generally, the upset drill pipe and tubing ends are bored and turned respectively by a boring head and a turning head. After the desired end portion of the upset pipe end has been bored and/or turned, the boring and/or turning tool must then be retracted from the pipe end. However, if the boring and turning tools are retracted, the machined surfaces are scarred or scratched by the cutting elements thereby providing unacceptable defects in the finished pipe end. To avoid this, the machine operator will back-bore in the direction opposite to that of the first boring operation (he will feed the tools in the reverse direction and bore again while retracting the tools from the pipe end), thereby doubling the required production time for boring and turning an upset pipe end.
In addition, other defects are created in the upset pipe ends after the boring and turning operations are completed, as many times sharp annular shoulders or steps are left on the inside and/or outside of the pipe end. These shoulders are undesirable as they produce stress concentration areas which are particularly susceptible to the effects of corrosion. These defects are unacceptable for use as drill pipe or tubing as in sour gas (H.sub.2 S) wells, for example.
It is a principal object of the present invention to eliminate these aforementioned disadvantages of the prior art.